A novel phosphoinositide-specific phospholipase C (TcPI-PLC) has been identified ii the protozoan parasite Trypanosoma cruzi, the etiologic agent of Chagas' disease. The gent (TcPI-PLC) encoding this enzyme was cloned, sequenced, expressed in E. coli, and the protein product was shown to have enzymatic characteristics similar to other PI-PLCs. However, this enzyme is the only known P1-PLC that is lipid modified by N-myristoylation and S-palmitoylation and could represent the first member of a new group of FI-PLCs. In contrast to other PI-PLCs described so far, the deduced amino acid sequence of TcPI-PLC revealed some unique features such as an N-myristoylation consensus sequence at its N-terminal end, lack o an apparent PH domain and a highly charged linker region between the catalytic X and Y domains. TcPI-PLC is lipid modified in vivo as demonstrated by metabolic labeling with (3H)myristate and (3H)palmitate and fatty acid analysis of the immunoprecipitated protein. The TcPI-PLC gene is developmentally regulated is expressed at high levels in the epimastigote and amastigote stages of the parasite, and its expression is induced during the differentiation of trypomastigotes into amastigotes. TcPI-PLC associates to the plasma membrane of amastigotes. Surprisingly, in addition to its role in generating the second messenger inositol1,4,5-trisphosphate (IP3) intracellularly, at certain time of their development the enzyme is also exposed to the extracellular medium of amastigotes where it could have potential novel roles in host-parasite interactions. Our hypothesis is that this enzyme is involved in the signaling cascades that take place during T. cruzi differentiation and host-parasite interactions. Our specific aims are to investigate: (1) the role of TcPI-PLC in differentiation of T. cruzi and its interactions with the host cells, and (2) the role of fatty acid modifications in TcPI-PLC localization and regulation of membrane binding.